Abstract: We present a new method for studying the subthreshold characteristics of nano-scaled MOSFETs,which we call the "regular perturbation method" . The Poisson equation is solved using this method for the first time.In particular,the depletion approximation and charge-sheet model in the Poisson equation are avoided due to their invalidity in nano-scaled MOSFETs.This yields a conventional exponential form of the subthreshold current,and the subthreshold swing can be obtained analytically from this current equation.The results of the model are compared and verified with the numerical simulation.

Key words: regular perturbation, surface potential, subthreshold swing, nano-scaled MOSFETs